Jimmy Fallon asked if the guys get along in real life. They joked that they hate each other, then Finn shared a story about hanging out Halloween night. They were supposed to watch scary movies, but when Finn showed up, they were watching "High School Musical."

Gaten said Sadie Sink -- who plays new character Max in "Stranger Things" Season 2 -- is a big fan of "High School Musical," and so is his own sister. So when Sadie started singing some "High School Musical" songs on set, that "opened the floodgates" in Gaten's memory and he found himself knowing every word.

Finn said the whole reason he played basketball is because of Zac Efron's character Troy Bolton. So he got up and briefly showed off his impression of Zac Efron's Troy.

Watch the impression around the 3:15 mark:Then Caleb slightly corrected Finn on how Efron held his head.